Lubrication liquids, commonly a lubrication oil or other oil such as hydraulic oil, are often used in mechanical systems, such as gear boxes, transmissions, hydraulic systems, motors, pumps, compressors, and generators to protect interacting component surfaces from excessive wear. To eliminate the metallic particles that become entrained within the oil due to components shedding, many mechanical systems include a filtering system in conjunction with the lubricating liquid flow path of the system to remove such debris. However, some systems are isolated such that filtration is impractical or impossible, and thus, oil circulates unfiltered. When not removed, these metallic particles will freely circulate through the system until they are finally removed when the oil is drained. These particles may cause damage.
One particularly harmful type of foreign matter in lubricating oil is small metallic magnetic particulates which are created by frictional contact between moving metal parts of mechanical systems. The magnetic particulates are shards of metal from the metal parts of the mechanical system that are dislodged during operation. As oil is circulated to lubricate the various moving components, the metallic particles entrained in the oil are carried to be unwittingly interfaced between the moving components. At these locations, the hardness of the metallic magnetic particulates causes metal to bear against metal, and reliance is placed solely on the oil to maintain a lubricating film. When these metallic magnetic particulates are brought to the interfaces, damage to the adjoining surfaces is likely. This damage eventually results in a degradation of the close tolerances between the moving parts, causing a loss in operating efficiency and more frequent maintenance in the form of repairs. By some estimates, these metallic magnetic particulates are the cause of more than one-half of the wear in said systems.
Two solutions exist for removing these metallic particles from a closed lubrication system of mechanical systems. The first solution involves the permanent installation of a permanent magnet within the lubrication compartment to attract and hold magnetic particles until a later date at which they can be removed, such as a complete rebuild of the mechanical system. The second solution is to install a magnetic drain plug in the housing of the power transmission unit. The magnetic drain plug attracts magnetic particles in the vicinity of the plug as the lubricant passively travels by the device.
Magnetic drain plugs have existed for quite some time with the most common being similar in form to those outlined in U.S. Pat. Nos. 5,949,317 and 5,420,557 which simply have a small magnet fastened on the end or nested inside of the drain plug. Several disadvantages exist with such designs. First, the magnet does not project far beyond the plug and has limited surface area for particle capture. Second, the magnet does not extend very far into the liquid reservoir and therefore experiences limited exposure to the lubricant entraining the magnetic particles flowing throughout the mechanical system. Finally, when the mechanical systems are running, the flow of liquid throughout travels at a very high flow rate, so a common problem is the plug's inability to hold onto the magnetic particles during operations. The only particles collected for removal are those gathered shortly before the drain plug is removed and when the system is turned off. These magnetic drain plugs fail to provide significant functionality when needed the most.
Another magnetic bolt assembly is found in U.S. Pat. No. 5,564,526 which involves the installation of a magnetic attachment over the external head of a steel drain plug. The magnetic flux coming from the magnetic attachment is channeled through the steel drain plug and creates a magnetic field on the opposite end of the plug which is exposed to the lubricant reservoir. This design places the source of the magnetic field on the outside of the lubrication reservoir and severely limits the attraction and capture of magnetic particles within the lubrication fluid.
Accordingly, what is needed is a device that may more aggressively capture magnetic particles generated during the normal operation of mechanical systems.